Exposure in utero to environmental chemicals such as polychlorinated biphenyls (PCBs) has led to documented examples of pediatric learning disorders including ADD, ADHD, and, perhaps, autism. Few embryo models exist which focus on the interaction of PCBs, regulatory genes such as the tumor suppressor gene family p53, and neuronal development. This two year R21 application addresses this issue using a marine invertebrate model. The surf clam, Spisula solidissima, has been used by embryologists to study distinct developmental stages during embryogenesis. Within the last decade, a new family of proteins, the cyclins, was discovered first in Spisula and has now been detected in many invertebrate and vertebrate species. Using the same model system, we have quantified neuronal development using panels of antibodies which recognize neural cells and/or networks. (Kreiling et al., Early development of the serotonergic and dopaminergic nervous system in Spisula solidissima (surf clam) larvae, Comp. Biochem. Physiol., 2001, 130: 341-351). We have further demonstrated that PCB exposure results in suppressed neural development (Kreiling et al., PCBs are selectively neurotoxic to the developing Spisula solidissima embryo. J. Tox. Env. Health 2000, 61: 657-675). Recently we have used Spisula to examine how the p53 gene family is expressed during development and, more importantly, have shown that PCB exposure regulates a specific p53 gene as well as protein expression. (Jessen-Eller et al., in the press, Environmental Health Sciences, 2002). Our preliminary data show that p53 gene family members may control development in Spisula. Based upon these new data, the primary purpose of this application is to define the role of four p53 genes, to investigate the differential expression of these four genes, and to define the impact of PCB exposure on their expression and function. We will employ molecular, immunochemical and microscopic approaches. Using cDNA and peptide antibodies that we have developed, we will focus on a novel, PCB sensitive member of the p53 gene family, PCB exposure and embryonic development. The work will have direct relevance to NIEHS, NIGMS, NINDS and NCI. Methods to be used include in vitro fertilization, confocal microscopy, 1 and 2-D gel electrophoresis, Northern hybridization, Western blotting, quantitative RT-PCR and in situ hybridization.